It failed to start up again yesterday, so I have been inside the cave of death again this morning.
I had a good look at the board and there is evidence of previous re-work. One of the ICs towards the rear of the board looks to have been replaced and possibly also the fuse holders for F1 and F2, as there is solder flux residue around these areas. I cleaned it up a bit, and re-flowed with new solder the F1 and F2 connections, as I wasn't getting a consistent continuity reading between the solder blobs of F2, the multimeter was giving a scratchy squeak instead of a constant tone. Previously I had tested the fuse holder terminals on the component side of the board only. After that the continuity reading was much better.
Though I have been minded to only change one thing at a time to hopefully better identify the exact fault and solution eventually, whilst I was in there I did what I had intended to do and replaced 4.7uF 35V cap C23 (with 50V part).
Now it's the waiting game again of periodic switching on to see if it fails to give a picture.
I really hope it's my imagination but it looks like the text isn't quite a well-focused as previously.
The only electrolytic now in the component number range C1-C34, which guesswork tells me are the ones associated with the power supply, which I haven't replaced is the big 100uF 400V C11. The replacements I've got won't fit as the "snap on" legs are the wrong pitch. I could probably make it fit if I had to. C11 may have been replaced before as there is a sticker with numbers including a date on the top of it, but there isn't the same evidence of rework on the solder side of the board as other components mentioned. The current one though is a 3-pin part.
I had a good look at the board and there is evidence of previous re-work. One of the ICs towards the rear of the board looks to have been replaced and possibly also the fuse holders for F1 and F2, as there is solder flux residue around these areas. I cleaned it up a bit, and re-flowed with new solder the F1 and F2 connections, as I wasn't getting a consistent continuity reading between the solder blobs of F2, the multimeter was giving a scratchy squeak instead of a constant tone. Previously I had tested the fuse holder terminals on the component side of the board only. After that the continuity reading was much better.
Though I have been minded to only change one thing at a time to hopefully better identify the exact fault and solution eventually, whilst I was in there I did what I had intended to do and replaced 4.7uF 35V cap C23 (with 50V part).
Now it's the waiting game again of periodic switching on to see if it fails to give a picture.
I really hope it's my imagination but it looks like the text isn't quite a well-focused as previously.
The only electrolytic now in the component number range C1-C34, which guesswork tells me are the ones associated with the power supply, which I haven't replaced is the big 100uF 400V C11. The replacements I've got won't fit as the "snap on" legs are the wrong pitch. I could probably make it fit if I had to. C11 may have been replaced before as there is a sticker with numbers including a date on the top of it, but there isn't the same evidence of rework on the solder side of the board as other components mentioned. The current one though is a 3-pin part.
Statistics: Posted by BeebMaster — Mon Dec 23, 2024 12:48 pm